Animation - Central (spinal) Mechanisms

This animation shows a simplified version of the relay of signals from incoming nerves to pathways which can take the signals up the spinal cord to further relays in the brainstem and from there to the cerebral cortex where they can be used to generate the experience of pain.
It shows how control signals from the brainstem can reduce or possibly stop signals reaching the brain by "blocking" transmission.
It also shows how two types of pain killing drug may reduce or stop signals reaching the brain by blocking transmission.